MS Access SQL Update with Minimum

Question

This SQL is beyond my expertise. I think it should be fairly easy for someone with experience. Here is what I have so far..

SQL is as follows:

UPDATE (Tbl_Stg_Project_Schedule_Dates 
INNER JOIN Tbl_Child_ITN ON   Tbl_Stg_Project_Schedule_Dates.ms_itn = Tbl_Child_ITN.ITN) 
INNER JOIN Tbl_Schedule ON Tbl_Child_ITN.Id = Tbl_Schedule.ID SET Tbl_Schedule.a_construction_start = [Tbl_Stg_Project_Schedule_Dates].[ms_start_date]
WHERE (((Tbl_Stg_Project_Schedule_Dates.ms_tempt_id) In (16,17,18,19,20,21,22,23)));

I want to add one last condition to this being that I only want the minimum of [Tbl_Stg_Project_Schedule_Dates].[ms_start_date] to update the table. I've tried the obvious of wrapping the field in Min, and also tried creating a separate aggregate select statement first (to get the min value with other criteria) that I then tried to create the update query from in new query but no luck.

Answer 1

I believe this is valid Access/Jet SQL. The idea here is to use a subquery to look up the earliest date among all the rows in your subset. I'm not sure if ms_itn was the right column to correlate on but hopefully you get the idea:

UPDATE (Tbl_Stg_Project_Schedule_Dates 
INNER JOIN Tbl_Child_ITN ON Tbl_Stg_Project_Schedule_Dates.ms_itn = Tbl_Child_ITN.ITN) 
INNER JOIN Tbl_Schedule ON Tbl_Child_ITN.Id = Tbl_Schedule.ID
SET Tbl_Schedule.a_construction_start = [Tbl_Stg_Project_Schedule_Dates].[ms_start_date]
WHERE (((Tbl_Stg_Project_Schedule_Dates.ms_tempt_id) In (16,17,18,19,20,21,22,23)))
and [Tbl_Stg_Project_Schedule_Dates].[ms_start_date] = (
    select min(sd.[ms_start_date])
    from [Tbl_Stg_Project_Schedule_Dates] as sd
    where sd.ms_itn = [Tbl_Stg_Project_Schedule_Dates].ms_itn
)